Recent Advances in Impurity-Induced Room-Temperature Phosphorescence

Abstract

Organic room-temperature phosphorescence (RTP) materials with large Stokes shifts and prolonged afterglows are gaining increasing attention in a variety of applications, including displays, anti-counterfeiting, sensing, and bioimaging. However, achieving high-performance organic RTP remains challenging due to weak spin-orbit coupling, rapid non-radiative decay, and unstable triplet excitons. Early studies focused on crystal engineering, as ordered lattices restrict molecular motion and stabilize triplet excitons. Analyzing crystal structures and packing provides valuable insights into intermolecular interactions, while theoretical calculations have clarified electronic structures, laying the foundation for rational RTP material design. However, recent findings suggest RTP in many single-component systems may arise from trace impurities, significantly influencing RTP properties. This discovery has greatly advanced the understanding of impurity-induced phosphorescence. This review systematically examines the role of impurities in RTP, detailing their origins from starting materials, solvents, and side reactions. It also explores how these identified impurities can serve as essential building blocks for designing new RTP materials. Finally, essential methods for evaluating compound purity, emphasizing the critical importance of rigorous analysis and validation are presented. Material purity plays a pivotal role in RTP research, as impurities can distort experimental data, potentially leading to misinterpretations that can impede advancements in understanding the underlying mechanisms.